Many RF/microwave applications require high power transistors, i.e., transistors having a power output of 5 watts or more. These high power transistors are typically housed in packages which include a mounting flange for mounting the package on a support, such as a metal heat sink, as well as an intermediate ceramic layer for bonding the transistor to the flange in an electrically insulating manner. Since power transistors of this type produce large amounts of heat, the flange, insulating ceramic and semiconductor must have an acceptable match of coefficients of thermal expansion to prevent de-lamination from thermal stresses encountered in normal operation.
Recently, new types of high power transistors have been developed for use in RF/microwave applications. In these transistors, the ground of the transistor is located in the lower major surface or "backside" of the transistor, opposite the upper major surface or "top" where the gate and drain are located. A transistor of this type is intended to be directly connected, electrically, to the base on which it is supported. However, at the present time, packaging assemblies ideally suited for housing such backside ground high power transistors have not been developed.
Accordingly, there is a need for a method of making a package ideally suited for housing high power, backside-ground transistors.